In recent years, there has been proposed to apply a bias voltage to a well where a transistor is formed.
By applying a bias voltage to a well where a transistor is formed, it is possible to adjust a threshold voltage of the transistor.
Further, there has been also proposed to apply bias voltages different from each other to wells of the same conductivity type that are electrically separated from each other.
[Patent Document 1] Japanese Laid-open Patent Publication No. 2008-277320
[Patent Document 2] Japanese Laid-open Patent Publication No. 2001-15695
[Patent Document 3] Japanese Laid-open Patent Publication No. 2002-134702
However, when the distance between the wells to which bias voltages different from each other are applied is made small in order to achieve miniaturization of a semiconductor device, a large leak current flows.